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"Childers, Daniel L."
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An integrated conceptual framework for long-term social-–ecological research
The global reach of human activities affects all natural ecosystems, so that the environment is best viewed as a social-–ecological system. Consequently, a more integrative approach to environmental science, one that bridges the biophysical and social domains, is sorely needed. Although models and frameworks for social-–ecological systems exist, few are explicitly designed to guide a long-term interdisciplinary research program. Here, we present an iterative framework, \"“Press-–Pulse Dynamics\"” (PPD), that integrates the biophysical and social sciences through an understanding of how human behaviors affect \"“press\"” and \"“pulse\"” dynamics and ecosystem processes. Such dynamics and processes, in turn, influence ecosystem services -–thereby altering human behaviors and initiating feedbacks that impact the original dynamics and processes. We believe that research guided by the PPD framework will lead to a more thorough understanding of social-–ecological systems and generate the knowledge needed to address pervasive environmental problems.
Journal Article
Stormwater Infrastructure Controls Runoff and Dissolved Material Export from Arid Urban Watersheds
Urbanization alters watershed ecosystem functioning, including nutrient budgets and processes of nutrient retention. It is unknown, however, how variation in stormwater infrastructure design affects the delivery of water and materials from urban watersheds. In this study, we asked: (1) How does stormwater infrastructure design vary over time and space in an arid city (Phoenix, Arizona, USA)?, and (2) How does variation in infrastructure design affect fluxes of dissolved nitrogen (N), phosphorus (P), and organic carbon (DOC) from urban watershed ecosystems? From 1955 to 2010, stormwater infrastructure designs shifted from pipes, to engineered channels and retention basins, to natural washes. We monitored 10 nested watersheds, where small (5–141 ha) watersheds had medium-density residential land use but differed in stormwater infrastructure, whereas larger watersheds (1,662–20,247 ha) had a variety of land uses and infrastructures. We measured rainfall in each watershed and discharge and dissolved N, P, and DOC concentrations in flow at each watershed outlet for runoff-generating rainfall events between 2010 and 2012. We used path analysis to test hypotheses about the relationships among infrastructure characteristics, land cover, storm characteristics (including antecedent conditions), and nutrient and DOC loads. We found that retention-basin density decreased and imperviousness increased runoff, which in turn increased nutrient and DOC delivery. Concentrations varied with antecedent conditions and rainfall but did not vary with watershed characteristics. We show that stormwater infrastructure creates heterogeneity in the hydrologic and biogeochemical function of urban watersheds and that stormwater management may represent a major source of ecosystem heterogeneity within and across cities.
Journal Article
Evolution and future of urban ecological science: ecology in, of, and for the city
The contrast between ecology in cities and ecology of cities has emphasized the increasing scope of urban ecosystem research. Ecology in focuses on terrestrial and aquatic patches within cities, suburbs, and exurbs as analogs of non-urban habitats. Urban fabric outside analog patches is considered to be inhospitable matrix. Ecology of the city differs from ecology in by treating entire urban mosaics as social-ecological systems. Ecology of urban ecosystems incorporates biological, social, and built components. Originally posed as a metaphor to visualize disciplinary evolution, this paper suggests that the contrast has conceptual, empirical, and methodological contents. That is, the contrast constitutes a disciplinary or \"local\" paradigm shift. The paradigm change between ecology in and ecology of represents increased complexity, moving from focus on biotic communities to holistic social-ecological systems. A third paradigm, ecology for the city, has emerged due to concern for urban sustainability. While ecology for includes the knowledge generated by both ecology in and ecology of, it considers researchers as a part of the system, and acknowledges that they may help envision and advance the social goals of urban sustainability. Using urban heterogeneity as a key urban feature, the three paradigms are shown to contrast in five important ways: disciplinary focus, the relevant theory of spatial heterogeneity, the technology for representing spatial structure, the resulting classification of urban mosaics, and the nature of application to sustainability. Ecology for the city encourages ecologists to engage with other specialists and urban dwellers to shape a more sustainable urban future.
Journal Article
Subjective evaluations of ecosystem services and disservices: an approach to creating and analyzing robust survey scales
Research on ecosystem services (ES) has largely focused on the ecological functions that produce services or the economic valuation of the benefits provided by ecosystems. Far less research has examined public perceptions of ES, and more so ecosystem disservices (EDS), despite evidence that ecosystem properties and functions can produce beneficial or detrimental outcomes for human well-being. To address this gap, we present a robust approach to measuring beliefs about ecosystem services and disservices. With various means to confirm the validity and reliability of ES and EDS measures, we demonstrate this approach with survey data that captures residents' perceptions about whether their local neighborhood environment (as the ecosystem of focus) provides certain positive or negative impacts in metropolitan Phoenix, Arizona. The results highlight patterns in people's views of: desirable and undesirable biota; benefits and risks pertaining to heat and stormwater; recreational and aesthetic values; and societal nuisances and problems. Composite survey scales for overall perceptions of services and disservices are presented, in addition to more distinctive dimensions of ES and EDS. To better understand and manage ecosystems for diverse benefits, the specific survey measures and the general methodological approach can be adapted to various ecosystems and contexts.
Journal Article
The relational shift in urban ecology: From place and structures to multiple modes of coproduction for positive urban futures
This perspective emerged from ongoing dialogue among ecologists initiated by a virtual workshop in 2021. A transdisciplinary group of researchers and practitioners conclude that urban ecology as a science can better contribute to positive futures by focusing on relationships, rather than prioritizing urban structures. Insights from other relational disciplines, such as political ecology, governance, urban design, and conservation also contribute. Relationality is especially powerful given the need to rapidly adapt to the changing social and biophysical drivers of global urban systems. These unprecedented dynamics are better understood through a relational lens than traditional structural questions. We use three kinds of coproduction—of the social-ecological world, of science, and of actionable knowledge—to identify key processes of coproduction within urban places. Connectivity is crucial to relational urban ecology. Eight themes emerge from the joint explorations of the paper and point toward social action for improving life and environment in urban futures.
Journal Article
A Decade of Ecosystem-Scale Research at an Aridland Constructed Treatment Wetland
Cities are increasingly pursuing more resilient and sustainable futures. One way to do so is by the increased use of Urban Ecological Infrastructure (UEI), including constructed treatment wetlands (CTW). This strategy is particularly important for aridland cities with scarce water resources. In this paper I synthesize nearly ten years of systems-level research at the Tres Rios CTW in Phoenix, AZ USA. Since July 2011, a research team that includes dozens of student volunteers has been sampling monthly for herbaceous biomass and productivity, water quality, transpiration rates, and aquatic metabolism. We also quantify belowground biomass and plant tissue nutrient content annually, and measured greenhouse gas fluxes from 2012 - 2014. Our peak summer biomass values are among the highest reported in the literature, and high rates of transpiration are associated with this biomass. Using our whole-system water budgets and tracer studies we have documented a slow movement of surface water into the marsh from adjacent open water areas that is driven by transpirational losses and that we refer to as the “biological tide”. With our nitrogen (N) budgets for the whole system and the vegetated marsh we showed that roughly 50% of the annual N uptake by the vegetated marsh is driven by new water entering via this biological tide. Our aquatic metabolism sampling suggested that the N uptake associated with the autotrophic water column was roughly 27% of the average annual N uptake by the vegetated marsh. The marsh is a source of CH4 and N2O across the air-water interface and the plants are a net source of CH4 but a net sink for N2O. Our combined flux estimates suggest that the Tres Rios marshes are a net sink for greenhouse gas equivalents because of this plant-mediated net uptake of N2O. Finally, over the years our Tres Rios CTW project has provided a platform for dozens of students and young people to experience ecological research, both in the field and in the lab.
Journal Article
Urban Ecological Infrastructure: An inclusive concept for the non-built urban environment
It is likely that half of the urban areas that will exist in 2050 have not yet been designed and built. This provides tremendous opportunities for enhancing urban sustainability, and using “nature in cities” is critical to more resilient solutions to urban challenges. Terms for “urban nature” include Green Infrastructure (GI), Green-Blue Infrastructure (GBI), Urban Green Space (UGS), and Nature-Based Solutions (NBS). These terms, and the concepts they represent, are incomplete because they tend to reduce the importance of non-terrestrial ecological features in cities. We argue that the concept of Urban Ecological Infrastructure (UEI), which came from a 2013 forum held in Beijing and from several subsequent 2017 publications, is a more inclusive alternative. In this paper we refine the 2013 definition of UEI and link the concept more directly to urban ecosystem services. In our refined definition, UEI comprises all parts of a city that support ecological structures and functions, as well as the ecosystem services provided by UEI that directly affect human outcomes and wellbeing. UEI often includes aspects of the built environment, and we discuss examples of this “hybrid infrastructure”. We distinguish terrestrial, aquatic, and wetland UEI because each type provides different ecosystem services. We present several examples of both “accidental” UEI and UEI that was explicitly designed and managed, with an emphasis on wetland UEI because these ecotonal ecosystems are uniquely both terrestrial and aquatic. We show how both accidental and planned UEI produces unexpected ecosystem services, which justifies recognizing and maintaining both purposeful and serendipitous types of UEI in cities. Finally, we posit that by incorporating both “ecological” and “infrastructure”, UEI also helps to bridge urban scientists and urban practitioners in a more transdisciplinary partnership to build more resilient and sustainable cities.
Journal Article
Compositional aspects of herbaceous litter decomposition in the freshwater marshes of the Florida Everglades
Aims Litter decomposition in wetlands is an important component of ecosystem function in these detrital systems. In oligotrophic wetlands, such as the Florida Everglades, litter decomposition processes are dependent on nutrient availability and litter quality. The aim of this study was to assess the differences and changes in chemical composition of above- and belowground plant tissues at different stages of decomposition, and to compare them to organic matter accumulating in wetland surface soils. Methods To understand the chemical changes occurring during the early stages of litter decomposition in wetlands, short-term subaqueous decomposition patterns of above- and belowground tissues from Cladium jamaicense and Eleocharis cellulosa were investigated at two freshwater marsh sites in the Florida Everglades. The composition of litter at different stages of decomposition was compared to that of the two end-members, namely fresh plant tissues and soil organic matter (SOM), in an effort to assess both the gradual transformation of this organic matter (OM) and the incorporation of above- vs. belowground biomass to wetland soils. The chemical composition of the litter and of surface soils was assessed using solid-state 13C nuclear magnetic resonance spectroscopy. Results Decomposition indices (alkyl/O-alkyl ratio, Aromaticity index) of Cladium and Eleocharis leaves varied during incubation likely reflecting physical leaching processes followed by a shift to microbial decomposition. Overall, Eleocharis leaves were more labile compared to Cladium leaves. Relative to aboveground litter, the belowground biomass of both species was more resistant to degradation, and roots were more resistant than rhizomes. Compared to the observed early diagenetic transformations of the plant litter, the SOM is at a more advanced stage of degradation, suggesting that the decomposition of litter and belowground biomass prior to its incorporation into wetland soils requires longer degradation times than those applied in this study. Conclusions Litter decomposition in Everglades' freshwater marshes is driven by a combination of tissue quality and site characteristics such as hydroperiod and nutrient availability, ultimately leading to the accumulation of peat.
Journal Article
Linking Ecology and Economics for Ecosystem Management
This article outlines an approach, based on ecosystem services, for assessing the trade-offs inherent in managing humans embedded in ecological systems. Evaluating these trade-offs requires an understanding of the biophysical magnitudes of the changes in ecosystem services that result from human actions, and of the impact of these changes on human welfare. We summarize the state of the art of ecosystem services–based management and the information needs for applying it. Three case studies of Long Term Ecological Research (LTER) sites—coastal, urban, and agricultural—illustrate the usefulness, information needs, quantification possibilities, and methods for this approach. One example of the application of this approach, with rigorously established service changes and valuations taken from the literature, is used to illustrate the potential for full economic valuation of several agricultural landscape management options, including managing for water quality, biodiversity, and crop productivity.
Journal Article